Diesel Particulate Filters (DPF) are used on diesel engines to reduce emissions of particulate matter (soot) generated during a heterogeneous combustion process. These filters must be cleaned or “regenerated” when the filter is determined full of soot. An engine control system can estimate the DPF accumulation, and determine when the filter needs regeneration. Once the filter is determined to be full, the control system will enable regeneration by modifying the combustion process and/or injecting fuel into the exhaust system to increase the temperature of exhaust flowing into the DPF. The elevated exhaust temperatures will initiate oxidation of the stored soot within the DPF.
Normally, this process is well controlled, and results in acceptable filter temperatures and durability. However, under some conditions the filter can be overloaded with particulates or regenerated during conditions that result in run-away temperatures. These excessively high temperatures can result in filter failure due to cracking from thermal stress, or even melting of the filter substrate.
In order to improve DPF durability, peak temperatures within the DPF should be controlled. One method of controlling peak temperatures includes limiting particulate loading. This cannot always be guaranteed due to customer driving cycles, ambient conditions, and/or variations in engine operating modes. Another method includes limiting the heat input into the DPF by the fuel injection process. This too is not always effective, since the stored particulate mass is often sufficient to lead to highly exothermic reactions that can damage the DPF material.